The study of the influence of ZnCl2 content in a flux for brazing of Al-Mg alloys on its technological properties

Aluminum-magnesium alloys are ductile alloys with good weldability, corrosion resistance, and a high fatigue strength level. Aluminum-magnesium alloys contain up to 6 % magnesium. The higher its content, the stronger is the alloy. However, these alloys with high magnesium content are difficult to solder. Therefore, the task is to create flux compositions for high-temperature brazing of these alloys providing high-quality brazed joints. The work investigated the influence of the ZnCl2 activator on the technological properties of the flux. The authors tested the flux compositions with ZnCl2 content of 0 to 12 %. The tests were carried out on the AMg2 alloy using the AK12 solder. The authors evaluated the influence of ZnCl2 content on the spreading area of solder, the spreading uniformity, and the surface condition. The study revealed a significant increase in the spreading area of solder when introducing the ZnCl2 activator into the flux and the introduction of 4 % zinc chloride made it possible to increase the spreading zone of a solder drop by 50–55 %. The authors considered the samples brazed with a flux that did not contain ZnCl2 and using flux with the addition of 4 % ZnCl2. Activator content in the flux increased by 4 % before reaching 12 %. The study identified the strong interaction between the flux and the base metal with the release of gaseous products leading to the pore formation. As a result of the work, it was revealed that ZnCl2 significantly affects the flux properties, allowing increasing the solder spreading area; however, in the result of reactions with the formation of gaseous products, it can lead to the porosity of the brazed joint.